Certain magnetic nanoparticles produce substantial heat under high strength alternating magnetic fields. These particles will be introduced into the body such that they accumulate in cancerous tissues. Ovarian cancer is characterized by an abundance of immunosuppressive phagocytes. Nanoparticles are ideal agents for the purpose of targeting these phagocytes, rationalized as follows. First, even when metastatic, ovarian cancer is most frequently restricted to the peritoneal cavity. Nanoparticles are readily injected into the tumor-associated-phagocyte-rich ascitic fluid that irrigates multiple peritoneal tumor masses. Second , these abundant natural phagocytes are the target of our therapy. In the treatment of other metastatic diseases, nanoparticle uptake after intravenous injection by cells of the reticuloendothelial system limits tumor exposure and is an impediment to delivery of systemically administered nanoparticles. Here, the phagocytes are our target. Third, after nanoparticle uptake these phagocytes act as delivery vehicles , migrating into tumor masses where they may better exert a therapeutic effect treatment. Fourth, nanoparticle activation can transform these immunosupressive phagocytes into immunostimulating phenotype. Ovarian cancer is a disease that is often discovered at an advanced stage and is poorly served by current treatment options. Our approach is designed to engage and better enable the patients immune system to fight the disease.